Fluctuation properties of laser light after interaction with an atomic system: Comparison between two-level and multilevel atomic transitions

A Lezama (1) , R Rebhi (2, 3) , Anders Kastberg (4) , S Tanzilli (4) , R Kaiser (3, 5)

1 UDELAR - Universidad de la República [Montevideo]
2 CQT - Centre for Quantum Technologies [Singapore]
3 INLN - Institut Non Linéaire de Nice Sophia-Antipolis
4 LPMC - Laboratoire de physique de la matière condensée
5 LOD - Laboratoire Ondes et Désordre

The complex internal atomic structure involved in radiative transitions has an effect on the spectrum of fluctuations (noise) of the transmitted light. A degenerate transition has different properties in this respect than a pure two-level transition. We investigate these variations by studying a certain transition between two degenerate atomic levels for different choices of the polarization state of the driving laser. For circular polarization, corresponding to the textbook two-level atom case, the optical spectrum shows the characteristic Mollow triplet for strong laser drive, while the corresponding noise spectrum exhibits squeezing in some frequency ranges. For a linearly polarized drive, corresponding to the case of a multilevel system, additional features appear in both optical and noise spectra. These differences are more pronounced in the regime of a weakly driven transition: whereas the two-level case essentially exhibits elastic scattering, the multilevel case has extra noise terms related to spontaneous Raman transitions. We also discuss the possibility to experimentally observe these predicted differences for the commonly encountered case where the laser drive has excess noise in its phase quadrature.

Domaines: Physique Quantique [quant-ph]; Physique Atomique [physics.atom-ph]

A Lezama, R Rebhi, Anders Kastberg, S Tanzilli, R Kaiser. Fluctuation properties of laser light after interaction with an atomic system: Comparison between two-level and multilevel atomic transitions. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2015, 92, pp.033853. ⟨10.1103/PhysRevA.92.033853⟩. ⟨hal-01254347⟩